border-1px($color)
    position:relative
    &:after
        display:block
        position:absolute
        left:0
        bottom:0
        width:100%
        border-top:1px solid $color
        content:''
        
border-none()
    &:after
        display:none


bg-image($url)
    background-image:url($url+"@2x.png")
    @media(-webkit-min-device-pixel-ratio:3),(min-device-pixel-ratio:3)
        background-img:($url+"@3x.png")